Some global properties of the attractive Hubbard model in the superconducting phase: theT-matrix approximation in two dimensions

Abstract
We have applied the fast Fourier transform, which allows one to compute efficiently convolution sums, to solve the set of self-consistent T-matrix equations to get the Green function of the two-dimensional attractive-U Hubbard model below , extending previous calculations by the same authors. Using a constant order parameter , we calculated as a function of the electron density and interaction strength U. These global results deviate from the BCS behaviour remarkably.
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